1. Field of the Invention
The present invention relates to a toner, a method of manufacturing the toner, a two-component developer, a developing device, and an image forming apparatus.
2. Description of the Related Art
Electrophotographic image forming apparatuses have been widely used as copiers so far, and in recent days, also as printers, facsimile machines, and the like equipment along with spread of computers since the electrophotographic image forming apparatus operates excellently as output units for computer images created by computers. In a general electrophotographic image forming apparatus, a desired image is formed on a recording medium through a charging step, an exposing step, a developing step, a transferring step, a fixing step, and a cleaning step. In the charging step, a photosensitive layer on a surface of a photoreceptor serving as an image bearing member is homogeneously charged. In the exposing step, the charged surface of the photoreceptor is irradiated with signal light corresponding to an original image so that an electrostatic latent image is formed. In the developing step, an electrophotographic toner (hereinafter referred to simply as “toner”) is supplied to the electrostatic latent image on the surface of the photoreceptor so that the electrostatic latent image is formed into a visualized image. In the transferring step, the visualized image on the surface of the photoreceptor is transferred onto a recording medium such as paper or OHP sheet. In the fixing step, the visualized image is fixed onto the recording medium by heat, pressure, etc. In the cleaning step, a toner and other matters remaining on the surface of the photoreceptor from which the visualized image has been transferred, are removed by a cleaning blade, and the surface of the photoreceptor is thus cleaned. Note that the visualized image may be transferred onto the recording medium by way of an intermediate transfer medium.
In the meantime, various techniques for computers have been further developed. For example, definition of computer images becomes higher and higher. This raises a demand on the electrophotographic image forming apparatus to form high-definition images almost equivalent to the computer images by reproducing tiny shapes, slight hue variation, etc. of the computer images precisely and clearly. In response to the demand, the development of definition of the electrostatic latent images has been accelerated and accordingly, with the aim of accurately reproducing high resolution electrostatic latent images, various techniques have been proposed to enhance properties of the developer which is to be attached to the recording medium, for example, to enhance image resolution, image sharpness, etc. In especially a large number of techniques proposed as above, toner particles are reduced in diameter to thereby enhance image quality. There have been thus various studies on the manufacture of a toner having small particles. The toner having small particles is useful for formation of high resolution images, but disadvantageous in that the fluidity of the toner is low since a large amount of particles of the toner have a volume average particle size of 4 μm or less.
The toner particles having a great impact on the toner fluidity, the image resolution, and the image sharpness are 7 μm or more and 5 μm or less in volume average particle size. It is therefore necessary to control a content of the toner particles having a volume average particles size of 7 μm or more and 5 μm or less in order to form high-quality images having sufficiently high definition and high resolution with toners excellent in the fluidity.
The color toner disclosed in Japanese Unexamined Patent Publication JP-A 7-146589 (1995), for example, has particles having a weight average particle size of 3 μm to 7 μm. The particles contain 10% by number to 70% by number of color toner particles of 4.00 μm or less, 40% by number or more of color toner particles of 5.04 μm or less, 2% by volume to 20% by volume of color toner particles of 8.00 μm or more, and 6% by volume of color toner particles of 10.08 μm or more, Tinting strength of the color toner is such that image density (D0.5) with the toner fixed is 1.0 to 1.8 when an amount (M/S) of unfixed color toner on a transfer member is 0.50 mg/cm2.
Although the color toner of JP-A 7-146589 contains 40% by number or more of color toner particles of 5.04 μm or less and 2% by volume to 20% by volume of color toner particles of 8.00 μm or more, such contents are not enough to provide the toner with favorable fluidity, resulting in a failure to form high-quality images having sufficiently high definition and high resolution.